James Cagney was wrong when he called a rival a “dirty, yellow-bellied rat” in the popular 1930’s film “Blonde Crazy.”

According to Time Healthland, a new study shows that rats aren’t really rats after all.

In the study, same-sex rats were housed in pairs in a cage for two weeks. During the testing sessions, one rat was set free, while the other was confined in a plastic restraining tube. The restraining device was designed for the free rat to be able to free the trapped one, if only it could figure out how to open the door.

In control conditions, the restrainer was empty or contained a toy rat.

According to researchers, the free rats immediately aided their trapped friends, once they learned how to open the door. It usually took about a week. Rats exposed to empty restrainers or a trapped toy rat ignored them.

"They are very smart and figure out if they pitch their nose up, they can open the door," says Jean Decety, the study’s senior author and Professor Psychology and Psychiatry at the University of Chicago. "It's not easy and it doesn't happen by chance. They try hard and circle around."

Researchers did not teach the rats how to open the door and they were given no incentive.

The research also suggests female rats show more empathetic behavior than male rats because all of the female rats learned to open the door to free their partners whereas 17 of the 24 males did.

Researchers then decided to test the rat’s perceived altruism by placing free rats in a cage with two restraining tubes. One contained a fellow rat, while the other contained chocolate chips to test whether the rats would or open both doors and share.

Approximately, 51 percent of the time, rats freed their mates and shared. They didn't take longer to release their mates even with the presence of the chocolate.

Researchers are also studying the biology underlying the rats’ “empathy- driven” actions by looking at chemicals such as the hormone oxytocin, which is involved in social bonding and nurturing behavior.

They hope the research can be translated into increasing the behavior among humans.

"There's no reason to think that only humans are pro-social and have empathy," says Decety.

Nor is there reason, she says, to believe that we are "naturally selfish.”

"We're a social species," says Decety. "It's good for us to help, it makes us feel good, it's connected with dopamine and that's good for everybody."